1. Field of Invention
The present invention relates to harmonic generators, and more particular to higher order harmonic generators.
2. Related Art
In conventional harmonic generators, harmonics are produced by passing a sinusoidal signal through one or more non-linear devices, such as analog multipliers, to generate a series of harmonics of the input signal. The desired harmonic can then be isolated through filtering and amplification. When operated near the saturation level of the devices, high non-linearities can occur. Thus, one solution is to reduce the power of the signal (sometimes referred to as “back-off”) to operate the devices in a more linear region. However, this then requires circuits that are bigger and more expensive than what would normally be needed. Furthermore, using low power or voltage signals would require large gains to obtain desired high power outputs. The large gains would also be applied to offsets, resulting in large unwanted offsets, which in turn will generate more non-linearities.
One type of high-frequency harmonic generator, such as a microwave generator, use low-order multipliers cascaded and combined to produce the desired frequency. However, generating harmonics using a series of analog multipliers has its disadvantages. First, a DC offset voltage or signal is generated along with the harmonics at different frequency components. The DC signal has negative effects, such as degrading the performance and/or linearity of the next multipliers in the cascade, reducing the dynamic range of the desired signal by the amount of undesired DC voltage, and creating undesired cross products that might be larger than the desired harmonics. In addition, higher order harmonics cannot be properly generated using current harmonics generators.
Therefore, there is a need for a harmonics generator that overcomes the disadvantages discussed above with conventional generators.